1 / 31

Unit 4 Lesson 4 Volcanoes

Unit 4 Lesson 4 Volcanoes. Unit 4 Lesson 4 Volcanoes. Magma Magic. What is a volcano?. A volcano is any place where gas, ash, or melted rock come out of the ground. Many volcanoes are dormant , meaning an eruption has not occurred in a long period of time.

ldouglas
Download Presentation

Unit 4 Lesson 4 Volcanoes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Unit 4 Lesson 4 Volcanoes

  2. Unit 4Lesson 4 Volcanoes Magma Magic What is a volcano? • A volcanois any place where gas, ash, or melted rock come out of the ground. • Many volcanoes are dormant, meaning an eruption has not occurred in a long period of time. • Mt. St. Helens was classified as dormant until the 1980 eruption. It hadn’t erupted for 400 years before that. • Some volcanoes are extinct, meaning that volcanologists do not think it will ever erupt again. • Mount Buninyong in Australia is classified as extinct. The last eruption was 12,000 years ago.

  3. Unit 4Lesson 4 Volcanoes What is a volcano? • Volcanoes form as rock below Earth’s surface melts. The melted rock, called magma, is less dense than solid rock, so it rises to the surface. • Lava is magma that has reached Earth’s surface. Lava and ash erupt from a vent, or an opening of a volcano.

  4. Unit 4Lesson 4 Volcanoes What are the kinds of volcanic landforms? • The location of a volcano and composition of magma determine the type of volcanic landforms created. • Volcanic landforms include: • shield volcanoes • cinder cone volcanoes • composite volcanoes • lava plateaus • craters • calderas

  5. Unit 4Lesson 4 Volcanoes What are the kinds of volcanic landforms? • Volcanic mountains are built from materials ejected from a volcano. • The shape and explosiveness of a volcano depend on the lava’s viscosity, or resistance to flow. • Low viscosity lava flows easily, forms low slopes and erupts without large explosions • High viscosity lava does not flow easily, forms steep slopes and can erupt explosively. • Pyroclastic material, hot ash and bits of rock, may also be ejected into the atmosphere.

  6. Unit 4Lesson 4 Volcanoes What are the kinds of volcanic landforms? • Shield volcanoes are volcanoes with broad bases and gently sloping sides. • They are the result of mild eruptions and usually contain low viscosity lava.

  7. Shield Volcanoes

  8. Unit 4Lesson 4 Volcanoes What are the kinds of volcanic landforms? • Cinder cones are small volcanoes with steep slopes. • They are the result of explosive eruptions with high viscosity lava. They form from ash and pieces of solidified lava that fall around a small vent.

  9. Cinder Cone Volcanoes

  10. Unit 4Lesson 4 Volcanoes What are the kinds of volcanic landforms? • Composite volcanoesare built from alternating layers of hardened lava flows and pyroclastic material. • They are the result of explosive eruptions with high viscosity lava. They generally develop into large, steep mountains.

  11. Composite Volcanoes

  12. Unit 4Lesson 4 Volcanoes What are the kinds of volcanic landforms? • Fissure eruptions happen when lava flows from giant cracks, or fissures, in Earth’s surface. • Because fissures have no central opening, lava flows out the entire length of the fissure. • Fissure eruptions produce a flattened layer of cooled lava called a lava plateau.

  13. Volcanic Fissures

  14. Lava Plateaus

  15. Unit 4Lesson 4 Volcanoes What are the kinds of volcanic landforms? • A volcanic crateris an opening or a depression at the top of a volcano. • A crater is caused by eruptions. • Inside the volcano, molten rock can form an expanded area of magma called a magma chamber.

  16. Volcanic Craters

  17. Magma Chamber Magma Chambers Magma Chamber

  18. Unit 4Lesson 4 Volcanoes What are the kinds of volcanic landforms? • When the magma chamber empties, the roof of the chamber can collapse, leaving a large basin-shaped depression called a caldera.

  19. Calderas

  20. Unit 4Lesson 4 Volcanoes Eruption! Where do volcanoes form? • Tectonic platesare giant sections of lithosphere on Earth’s surface. Volcanoes can form at plate boundaries or within the middle of a plate.

  21. Unit 4Lesson 4 Volcanoes Where do volcanoes form? • At divergent plate boundaries, where two plates are moving away from each other, fissure eruptions are likely to occur. • At hot spots, which are far from any plate boundaries, shield volcanoes, fissure eruptions, and cinder cones can occur.

  22. Unit 4Lesson 4 Volcanoes Where do volcanoes form? • At convergent plate boundaries, composite volcanoes can occur. • Composite volcanoes produce the most violent eruptions. • The Ring of Fireis a name for the numerous explosive volcanoes that form on convergent plate boundaries surrounding the Pacific Ocean. 90% of all the volcanoes on the planet are located there.

  23. Unit 4Lesson 4 Volcanoes Where do volcanoes form? • At divergent boundaries, the crust stretches and gets thinner. • As a result, the pressure on the mantle rock below decreases, and magma rises through fissures in the lithosphere. • Divergent plate boundaries create fissure eruptions and shield volcanoes.

  24. Unit 4Lesson 4 Volcanoes Where do volcanoes form? • Most divergent boundaries are on the ocean floor. When eruptions occur in these areas, undersea volcanoes develop. • These volcanoes and other processes lead to the formation of a long, underwater mountain range known as a mid-ocean ridge.

  25. Unit 4Lesson 4 Volcanoes Where do volcanoes form? • When a divergent boundary is located in the middle of a continent, the crust stretches until a rift valley is formed.

  26. Unit 4Lesson 4 Volcanoes Where do volcanoes form? • At convergent boundaries, one plate usually sinks beneath the other. The mantle above the sinking plate can melt to form magma. • The magma rises to the surface and forms volcanoes.

  27. Unit 4Lesson 4 Volcanoes Where do volcanoes form? • Magma at convergent boundaries has a high concentration of fluids, which form gas bubbles. • Because the magma has a high viscosity, the bubbles cannot escape easily. As the bubbles expand, the magma rises faster. • Eventually, the magma erupts explosively, forming composite volcanoes or calderas.

  28. Unit 4Lesson 4 Volcanoes Where do volcanoes form? • Hot spots are locations far from plate boundaries where a mantle plume,a column of extremely hot mantle rock, rises and produces volcanoes.

  29. Unit 4Lesson 4 Volcanoes Where do volcanoes form? • Chains of volcanoes can form over time as a tectonic plate moves over a mantle plume.

  30. Unit 4Lesson 4 Volcanoes Living Near a Volcano • Many people around the world live near a volcano because the surrounding soils are fertile for growing a variety of crops. • Volcanic rocks can be used in making jewelry, concrete, water filtration systems, and other applications. • However, an eruption can produce destructive earthquakes, fire, ash, and lava flows, destroying property and taking lives.

More Related